iwlwifi: Move HBUS address to iwl-csr.h

HBUS is accessed through CSR registers
moved to iwl-csr.h

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>